Hydraulic pressing apparatus



Nov. 23, 1954 A. L. SCOTT HYDRAULIC PRESSING APPARATUS Filed Dec. 15. 1952 INVENTOR. ARTHUR L. SCOTT? mmTa United States Patent Ofiice 2,694,903 Patented Nov. 23, 1954 HYDRAULIC PRESSIN G APPARATUS Arthur L. Scott, Columbus, Ohio, assignor to The Denison Engineering Company, Columbus, Ohio, a corporation of Ohio Application December 15, 1952, Serial No. 326,025

Claims. (Cl. 60-97) This invention relates to hydraulically operated apparatus and more particularly to hydraulic systems for such apparatus.

An object of this invention is to provide a hydraulically operated pressing apparatus in which two rams are arranged in opposed registering relationship and operated to move toward and away from one another simultaneously to impart a pressing force to opposite sides of an article undergoing treatment, the rams being automatically con trolled and the control mechanism being hydraulically interlocked so that one control mechanism regulates the timing of both rams.

Another object of the invention is to provide a hydraulic system for two opposed rams, the system having valves formed in accordance with the disclosures of Patents No. 2,491,355 and No. 2,512,730, issued in the name of C. E. Adams on December 13, 1949, and June 27, 1950, respectively, the valves being hydraulically connected and operated simultaneously at predetermined times.

A further object of this invention is to provide a hydraulic pressing apparatus having a plurality of rams and a control mechanism for each ram, each control mechanism having a pressure responsive reversing valve, to govern the direction of movement of the ram associated therewith, and a hydraulic connection between the pressure responsive reversing valves so that they may be operated together whereby the rams will be caused to move or exert pressing forces simultaneously.

A still further object of the invention is to provide the apparatus, mentioned in the preceding paragraph, with a second pressure responsive valve for controlling the application of fluid pressure to the reversing valves of the control mechanism simultaneously, the second pressure responsive valve being so connected in the hydraulic system that it will be exposed to and operated by fluid pressure when one of the rams moves in a certain direction, the operation of the second pressure responsive valve serving to actuate both reversing valves to reverse the direction of movement of both rams, the control mechanism being so arranged that the second pressure responsive valve will be actuated immediately following the termination of a pressing stroke of one of the rams thus causing both rams to execute a series of short pressing and retractive motions which subject an article between the rams to a series of opposed pressing impulses; the mechanism'may be adjusted to cause these impulses to occur with suflicient rapidity as to resemble vibrations.

Another object of the invention is to provide a valve in the hydraulic connection between the pressure responsive reversing valves and to have such valve actuated by one of the rams at a predetermined stage of operation so that the second ram will be set in motion at the proper time to effect the end result desired.

A further object of the invention is to provide an electro-responsive valve in the hydraulic connection between the pressure responsive reversing valves and to dispose a control switch for the electro-responsive valve in the path of movement of one of the rams so that, when this ram reaches a predetermined position in its cycle of movement, the switch will be actuated to initiate a cycle of operation of the second ram; after the rams engage the work and exert opposed pressing forces of a selected tonnage thereon, the reversing valves will automatically reverse the direction of travel of the rams and they will retract from the Work and from one another, upon this initial retractive movement the second pressure responsive valve will operate to apply fluid pressure to the reversing'valves to cause the rams to resume advancing movement to again exert pressing forces on the work; this operation may be repeated as many times as desired or necessary.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of embodiment of the invention is clearly shown.

In the drawing, the single figure is a diagrammatic view of a hydraulic system formed in accordance with the present invention.

Referring more particularly to the drawing, the complete hydraulic system or circuit is designated by the numeral 20. This circuit includes two sections 21 and 22 and a single connecting fluid line 23. The circuit section 21 is substantially identical with the circuit disclosed in Patent No. 2,512,730 mentioned above while the circuit section 22 is substantially identical with the circuit in the other Patent No. 2,491,355. Each circuit controls the flow of fluid from a pressure source to a power cylinder, cylinder 24 being associated with the circuit 21 and cylinder 25 being associated with the other circuit. Each circuit includes a source of fluid pressure including a reservoir, a motor driven pump, and a relief valve. The reservoirs are shown in the drawing as two separate reservoirs for convenience in illustration. It should be obvious, however, that a single reservoir could be provided if desired. In the circuit 21, the pump is indicated by the numeral 26, the relief valve 27, and the reservoir 28. In circuit 22, numeral 30 indicates the pump, 31 the relief valve, and 32 the reservoir. For a more detailed description of the mechanism composing the circuits 21 and 22, reference may be had to the above-mentioned patents. Only a description suflicient to facilitate an understanding of the present invention will be given here.

Reference to the patents mentioned will disclose that the circuits 21 and 22 include automatic control valve mechanisms which are enclosed in single casings, the control mechanism in the circuit 21 being surrounded by a dotted line in the present illustration and the control mechanism in circuit 22 being enclosed by another dotted line.

The control mechanism for circuit 21 receives fluid from the pump 26 through a line 33 which extends to the inlet port 34 of a reversing valve designated generally by the numeral 35. This valve controls the flow of fluid from the pressure source to and from the power cylinder 24 to eifect the reciprocation of a piston 36 forming a part of the power cylinder 24. Piston 36 has a ram 37 secured thereto, this ram being reciprocated when the piston 36 moves in the power cylinder. Cylinder 24 is connected with the control mechanism by fluid conduits 38 and 40, the former extending to the upper end of the power cylinder 24 and the latter extending to the lower end thereof. Conduits 38 and 40 lead to top and bottom cylinder ports 41 and 42, respectively, of the pressure reversing valve, this valve also having exhaust ports 43, 44A and 44B formed therewith.

Port 44A communicates with an exhaust passage section which will cause exhaust fluid from the lower end of the power cylinder 24 to by-pass a flow control mechanism 48 While port 44B communicates with an exhaust passage section which directs fluid flow through the flow control.

Reversing valve 35 includes a sleeve-like ported element 45 and a fluid pressure responsive spool valve element 46 disposed within the sleeve-like element and movable between two extreme positions therein. A coil spring 47 tends to move the spool element 46 toward one position, the spool being moved in opposition to the coil spring by fluid pressure. Spool element 46 is shown, in the drawing, in the position occupied when fluid pressure is applied thereto. In this position, the valve establishes communication between inlet port 34 and the top cylinder port 41 and fluid from the pressure source may flow through the reversing valve to the upper end of the power cylinder. This fluid will be applied to the upper end of the piston 36 causing this member to move in a downward direction to extend the ram 37. When the piston initially moves in a downward direction, fluid beneath the piston flows through the exhaust line 40 to the exhaust port 42 and is directed by the valve element 46 to exhaust .nism 48.

-port .44Asand the exhaust. passagesection communicating therewith.

This passage section directs the fluid through the interior of the flow control valve spool, indicated by the numeral 48, and through a restricted port or orifice 50 therein to. an exhaust line 51 which extends back to the reservoir v23. The restricted port or orifice 50 creates a back pressure on the fluid flowing from the lower end of the power cylinder, which back pressure is directed through passage meansin the valve element 46 to the interior of the valve member to maintain the pressure which holdsthe valve element '46 elevated against the spring 47 and continues the connection between the fluid pressure source and the upper end of the power cylinder. ,Asllong as thisconnection is established, the piston 36 will. continue to move in a downward direction.

.As. explained in the second patent mentioned above, the engagement of the ram 37 with an obstruction offering .sufficient resistance to interruptan'd prevent further move- 'ment of the ram will cause the pressure inthe upper end of thepowercylinder and passages connected therewith to increase to the setting of the relief valve 27 and the ram will then be exerting the maximum tonnage for which therelief valvehas previously been set. Fluidfrom the :pressure source is initially supplied to the valve 46 to effect -its.movement to'the position shown in the drawing by the actuation of a manualcontrol spool'52. This spool -may be set in a number of desired positions, theposition shown providing for automatic repetition of the cycle of operation of the ram.'37. The ram 37 is disclosed in its .initial starting position wherein an arm 53 secured thereto :engages a collar '54'on a shipper rod '55 extending from the valve element 45 and holds this valve elementin an elevated position. "Inthis position, a portin the valve 45 registers-with a port 56 which is connected'to the chamber forthe valve 52 and serves to direct fluid from the pressure source through the chamber for valve 52 to the interior of the valveelement- 45 beneath the valve member 46. When the ram 37 moves to a predetermined power cylinder through port 443 to the section of the exhaustpassage, which includes the flow control mecha- Downward movement of the valve element 46 also interrupts the flow of fluid from the pressure source to port56 and flow of pressure from the pressure source to the lower end of the valve element 46. Since movement of the piston 36 in a downward direction causes a flow of fluid to exhaust which is opposed by the orifice to create back pressure and this back pressure is applied vto the lower end of the valve element 46, this element 'will remain in position to continue the flow of fluid from the .pressure source to the upper end of the power cylinder.

The section of the exhaust passage leading from port 443 includes a needle valve 58 which causes a pressure drop in the passage, the higher pressure of which is applied to the lower end of the flow control spool 48.. This .pressure willmove the flow control spool in opposition to itsspring to connect passage 33 directly with exhaust passage .51 so that some of the fluid flowing from the .pressure source will be by-passed around the power cylinder.24 causing a reduction in the rate of movement of .thepiston 36 and ram 37. This flow control mechanism .Ihas'becn described in detail in Patent No. 2,512,730 and .furtherdescription thereof at this time will be omitted.

When the movement of the ram 37 is interrupted, the

exhaust flow from the lower end of the power cylinder will stop. At this time, the back pressure in the exhaust line will'be dissipated and spring 47 will return valve element 46 to its lower position wherein the source of fluid pressure will be connected with the lower end of the power cylinder and fluid under pressure will be applied to the bottom of piston 36. This fluid will tend to move the piston in an upward direction to cause the retraction of the ram 37. Control mechanism 21, however, is provided with another pressure responsive valve 69 which is disposed for'movement in a bore connected by a passage 61 to theconduit 40 extending to the lower end of the power cylinder. When conduit 40 is connected with the pressure source by the movement of the valve spool 46 toits lower position, fluid pressure will also flow through line 61 to the underside of valve 60. This fluid pressure will move the valve in an upward direction to a posi- 4 tion in which communication is established between line 33 and a line 62 extending to the bore for the valve member 45. This valve member has a port which permits the fluid pressure flowing through line 62 to enter the space beneath the valve 46 which valve will be moved again to its upper position by such fluid pressure.

As previously pointed out, valve 46 will connect the upper end of the power cylinder 24 with the pressure source when such valve is in its elevated position. Of course, the upward movement of valve 46 establishes a connection between'the lower end of the power cylinder 24 and the exhaust passage and fluid pressure flowing to the upper end of the power cylinder will cause the piston 36' and ram 37 to resume movement in a downward or advancing direction. The distance piston 36 is permitted to move in a reverse direction prior to the resumption of forward movement will depend upon the rate at which valveelement 60 is, permitted to move to a position establishing communication betweenpressure line 33 and pets sage'62. -The rate of movement of valve 60 is controlled by a needle valve 63 which is disposed in a passage extending from the chamber'containing'valve 60 to a passage 64 which leads to one end of a chamber 65 containing a spring pressed valve spool'66. The passage 64 communicates with a chamber 67' in which a piston 68 is disposed for movement. This piston serves to displace a fixed quantity offluid each time the valve 60 is operated. The fluid displaced by piston 68 accumulates in the chamber"65 and causes the spool 66 to be depressed step by step against the action of its spring until the spool 66 moves to a'positionto prevent communication between lines 33 and 62.

When this communication is interrupted, the reverse movement of 'piston 36will continue until the ram 37 is fully retracted. As pointed out, thiscomplete retraction of the ram causes the arm 53 to engage the collar 54 and move the shipper rod 55'and valve element 46 to an upper position. Whenvalve element moves to this upper position, it actuates a check valve 70 which controls fluid flow through'an exhaust line 71 extending from the chamber'65. When valve 70 is open, the spring for spool 66 will return'this spool to its initial position thus setting spool 66, piston 63 and valve 60 for'the next cycle of operation.

'It will be obvious from the foregoing and an inspection of PatentNo. 2,512,730 that the control mechanism 21 will cause the piston 37' to operate through a cycle including an initial advancing stroke, a series of short reciprocatory strokes, the number of which depends upon the position of valve spool'66, and then retraction to its initial starting position. The length and rapidity of the short reciprocatory strokes may be controlled by. the adjustment of the valve 63. The number of such strokes may be controlled through the adjustment of screw 72, this screw constituting the mechanism for regulating the initial starting position of the valve spool 66.

The control mechanism in circuit 22 is substantially identical with the control mechanism in circuit 21 with the exception of the flow control mechanism and the mechanism for causing the short reciprocatory strokes of the ram. The control mechanism in circuit 22 includes a reversing valve having a ported sleeve-like spool 73 and .a pressure responsive spool 74 disposed for movement within the sleeve 73. The control mechanism in circuit 22 is inverted because it controls the movement of a piston 75 and ram76 forming part'of the power cylinder 25, the ram 76 being disposed in inverted or opposed relationship to the ram 37 and in alignment therewith. It is desired to cause the movement of ram'76 simultaneously with a portionof the movement of ram 37. In the employment of the hydraulic system forming the subject matter of this invention, the rams 37 and 76 are moved into engagement with opposite ends of an article or a body of material from which an article is to be formed. These rams may cooperate with a suitable forming die, the ram 76 being connection with a punch or other portion of the die which forms a bottom wall in a cavity for receiving material. 'It is desired to hold this bottom wall stationary until the cavity is filled with material and the ram 37 or a punch carried thereby enters the cavity in the die to confine the article forming material therein. The system is, therefore, provided with an electro-responsive valve. the flow ofcurrent to which is governed by a switch 77 disposed in the path of movement of an actuator 78 carried bv ram 37.

As in the control mechanism for ram 24, the reversing valve mechanism from power cylinder 25 controls the flow of fluid under pressure from the pressure source 30 to the power cylinder, the position of pressure responsive spool 74 determining the direction of movement of the piston 75 and ram 76. The control mechanism in circuit branch 22 is illustrated in position to maintain the piston 75 and ram 76 in fully retracted positions. The valve element 74 is shown elevated, to which position it has been moved by the coil spring 80. Valve spool 73 is disposed in its lower position to which it has been moved by the retraction of ram 76, this ram having an arm 81 which engages a collar 82 on a shipper rod 83 extending from the valve member 73. Fluid to operate the power cylinder 25 is supplied by pump 30 through line 84 which extends to inlet port 85 of the reversing valve 73, 74. With the valve elements in the positions shown, fluid from the pressure source will be directed through a bore 86 containing a spool 87 to an exhaust line 88 leading back to the reservoir 32. The spool 87 may be manually moved between a number of positions, the spool being shown in position to cause the automatic operation of the power cylinder 25, when the power cylinder 24 is operated.

In the position of spool 87 illustrated, a land 90 thereon blocks a groove 91 from communication with the bore 86. Groove 91 communicates with a groove 92 surrounding the bore for the spool 73. These grooves are both connected with the line 23 extending from the control valve mechanism 21, the line 23 communicating with the portion of the bore for valve element 45 which is connected with line 62. Line 23 contains an electroresponsive valve 93 which, when de-energized, establishes communication between branch 23A of line 23 and an exhaust line 94 leading to the reservoir 32. The valve 93 contains a spool element 95 which, when the valve is de-energized, occupies the position shown in the drawing in which, as previously mentioned, line 23A is connected with the reservoir. When this connection is established, grooves 91 and 92 will contain fluid under tank pressure. When ram 37 moves to a position to cause switch 77 to close, the electro-responsive valve 93 will be energized and valve spool 95 will be moved to the left to establish communication between branch lines 23 and 23A and fluid under pressure will then flow from the control valve mechanism for power cylinder 24 to the grooves 91 and 92. This fluid pressure will flow through ports 96 formed in spool 73 and be applied to the upper end of valve spool 74. This fluid pressure will move the valve spool against the action of spring 80 to its lowermost position in which communication will be established between line 84 and line 97 leading to the lower end of power cylinder 25. Fluid introduced into the lower end of the power cylinder will cause piston 75 to move in an upward direction, which movement will cause the discharge or exhaust of fluid from the upper end of power cylinder 25 through line 98. This line will be connected by valve spool 74 with exhaust line 88 which leads to the reservoir 32. Valve spool 74 differs from valve spool 46 in that the former has a restricted passage 74A therein through which the exhaust fluid of power cylinder 25 flows. The restriction in this passage causes a back pressure which is applied through a port 74B in the upper portion of the spool 74 to the upper end of the spool, this back pressure serving to retain the spool 74 in its lowered position against the action of spring 80.

When ram 76 moves in an upward direction, arm 81 will move away from collar 82 permitting a spring in the valve mechanism to move the spool 73 upward until the registration of port 100 in spool 73 with groove 101 in the casing of valve mechanism is interrupted. As previously mentioned, it is desired to permit ram 37 to move through a portion of its advancement before operation of ram 76 is initiated. The location of switch 77 will determine the distance travelled by the ram 37 before operation of ram 76 is initiated. After switch 77 is actuated, ram 76 will move toward ram 37 and an article, or material to form the same, will be subjected to opposing forces applied to opposite ends thereof. When the material or the article has been compressed under the force determined by the relief valves 27 and 31, both rams will stop moving. The valves 46 and 74 will then be actuated by their springs to move to positions to cause the reverse movement of the rams 37 and 76. The initial reverse movement of ram 37 will cause the actuation of pressure valve 60 and fluid from the pressure source will be directed through line 62 to the space beneath valve element 46. This fluid pressure will also be conducted through lines 23 and 23A to the space above valve spool 74.

It will'be obvious to those skilled in the art that the application of fluid pressure to the valve elements 46 and 74 will occur simultaneously and these valve elements will move to positions to cause the rams 37 and 76 to resume advancing motion. This motion of the rams will subject the material between them to another pressing action applied to both ends of the material. These applications of force by both rams will be repeated until valve spool 66 moves to a position to interrupt communication between fluid passage 33 and line 62 as previously described. When this interruption to fluid flow to line 62 occurs, both rams will return to their retracted positions for the completion of the cycle of operation. When ram 37 retracts a sufiicient distance, switch 77 will move to an open position, de-energizing valve 93 which will izrgtzrrupt communication between branch lines 23 and If the rams 37 and 76 have been forming an article in a die, ram 76 may then be operated through the actuation of spool 87 to perform an article ejecting stroke. Valve spool 87 may be manually operated to move to a position in which land 102 thereon will prevent the exhaust of fluid from the pressure source and direct such flow to groove 91 from which it will flow through groove 92 and ports 96 to the space above valve element 74. This fluid pressure will move the valve element, as previously described, to a position wherein the source of fluid pressure is connected with the lower end of the power cylinder 25. Ram 76 will be extended to eject the formed article from the die mechanism. The distance moved by ram 76 will be determined by the setting of a collar 103 on the shipper rod 83. When this collar is engaged by the arm 81, the ram will move the sleeve valve 73 to a position in which a relieved portion 104 adjacent the lower end thereof establishes communication between the lower end of the power cylinder and the exhaust line 88. The establishment of this connection interrupts the movement of the ram toward a fully extended position and interrupts also the exhaust of fluid from the upper end of the cylinder 25. The back pressure will be dissipated permitting spring 80 to return valve element 74 to its elevated position in which the source of pressure 30 is connected with the upper end of the power cylinder. The establishment of this connection will cause a retraction of ram 76 as previously described. Spool 87 need be moved to the position establishing communication between groove 91 and bore 86 only momentarily to effect the extension of ram 76. After this movement has been initiated, spool 87 may be returned to the position shown. The cycle of movement of ram 76 will be continued automatically and, when it is retracted, the mechanism will be in condition for the next cycle of operation of the complete system shown.

The valve spool 52 of the control mechanism for cylinder 24 must be returned to a position in which a land 105 thereon will prevent the flow of fluid from the pressure source 26 through the groove 56 to the underside of valve 46 after the operation of power cylinder 24 has been initiated if it is desired to eject the formed article in the manner described. Otherwise the cycle of operation of power cylinder 24 will be automatically repeated upon completion of the retractive movement of ram 37. In some instances, it may be desirable to cause the automatic repetition of the cycles of operation of power cylinders 24 and 25 without the ejecting operation of ram 76. If such an operation is desirable, valve spool 52 may be moved to and retained in the position shown in the drawing. Then, when ram 37 is almost fully retracted, the engagement of arm 53 with collar 54 will move valve sleeve 45 to the position shown in which the source of fluid pressure 26 is directly connected with the space at the lower end of valve element 46.

It will be obvious from the foregoing that a hydraulic system has been provided with which a pair of opposed registering rams may be caused to move toward one another and engaged with an article, then operate to impart to such article a series of pressing impulses applied to opposite ends of the article, the rams being retracted upon completion of such series of pressing impulses. The mechanism may be adjusted todetermine the rapidity of pressing impulses as well as the number thereof. The mechanismmay also be operated to cause the ejection of a formed article from the forming dies.

In the formation of articles with apparatus of the type shown and described herein, it has been observed that a limited amount of movement of the article relative to the mold during the application of forming pressure prouuces a superior finish on the mold engaging sides. By utilizing a greater force on one of the rams, this relative movement, during article formation, may be secured. To this end, it is within the concept of the invention to operate the power cylinder 24 under a slightly greater pressure which will result in the ram 37 causing the ram v76 to move backward or downward after the material in the mold has been partially compressed therebetween. This limited movement occurs each time the rams move in the material compressing strokes and, therefore, on each short pressing impulse or so-called vibration. It may also be found desirable to alternatively employ a higher pressure, to operate the power cylinder 25 to secure the relative movement between the article and the mold wall. The results will be substantially identical with those secured when the higher pressure is used in the other power cylinder. Through the'adjustment of the control mechanism, the portion of the mold in which the relative movement ,of the article takes place may be adjusted to counteract wear and premature deterioration of the mold.

While the form of embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

I claim:

1. A hydraulic system comprising a pair ofpower cylinders with opposed rams; a source of fluid pressure; control valve mechanism between the pressure source and each power cylinder, each control valve mechanism having a fluid'pressure responsive reversing valve element; additional valve means for simultaneously effecting the application of fluid pressure to the fluid pressure responsive reversing valve element of both control valve mechanisms; and means responsive to the movement of one of said rams to actuate said additional valve means.

2. A hydraulic system comprising a pair of power cylinders with opposed rams; a source of fluid pressure; a control valve mechanism between the pressure source and each power cylinder, each control valve mechanism having a fluid pressure responsive reversing valve element; an additional valve member for simultaneously effecting the application of fluid pressure to the fluid pressure responsive reversing valve elements of both control valve mechanisms; and means operative when one of said rams reaches a predetermined position to actuate said additional valve member.

3. A hydraulic system comprising a pair of power cylinders with opposed rams; a source of fluid pressure; a control valve mechanism between the pressure source and each power cylinder, each control valve mechanism having a fluid pressure responsive reversing valve element; another valve member for effecting the application of fluid pressure to the fluid pressure responsive reversing valve element of one of said valve mechanisms to cause the operation of the ram of the power cylinder controlled thereby; and valve controlled passage means rendered operative by the last named ram at a predetermined stage of operation to establish a hydraulic connection between said pressure responsive reversing valve elements to elfect simultaneous operation thereof.

4. A hydraulic system comprising a pair of power cylinders with opposed rams; a source of fluid pressure; a control valve mechanism between the pressure source and each power cylinder, each control valve mechanism having a fluid pressure responsive reversing valve element; another pressure responsive valve member for effecting the application of fluid pressure to the fluid pressure responsive reversing valve element of one of said valve mechanisms to cause the operation of the ram of the power cylinder controlled thereby; a valve controlled passage establishing a hydraulic connection between the pressure responsive reversing valve elements of said control valve mechanisms; and means operated by the lastmentioned ram at a predetermined stage of operation. to render said valve controlled passage effective.

5. A hydraulic system comprising a pair of power I cylinderswith opposedrams; a sourceof fluid pressure; a control valve mechanism between the pressure/source:

and each power cylinder, each control valve mechanism having a fluid pressure responsive reversing valve element; another pressure responsive valve member for effecting the application of fluid pressure to the fluid pressure responsive reversing valve element of one of said valve mechanisms to cause the operation of the ram of the power cylinder controlled thereby; a passage extending between the pressure responsive reversing valve elements of said control valve mechanisms; a valve element in said passage; and means actuated by the lastmentioned ram at a predetermined stage of operation thereof to open said valve to establish a hydraulic connection between said pressure responsive reversing valve elements.

6. A hydraulic system comprising a pair of power cylinders with opposed rams; a source of fluid pressure; a control valve mechanism between the pressure source and each power cylinder, each control valve mechanism having a fluid pressure responsive reversing valve element; another pressure responsive valve member for effecting the application of fluid pressure to the fluid pressure responsive reversing valve element of one of said valve mechanisms to cause the operation of the ram of the power cylinder controlled thereby; a passage extending between the pressure responsive reversing valve elements of said control valve mechanisms; an electroresponsive valve element in said' passage; and switch means actuated by the last-mentioned ram at a predetermined stage of movement'thereof to energize said electroresponsive valve and establish a hydraulic connection between said pressure responsive reversing valve elements.

7. A hydraulic system comprising a pair of power cylinders with opposed rams; a source of fluid pressure; a control valve mechanism between the pressure source and each power cylinder, each control valve mechanism having a reversing valve element responsive to fluid pressure to move to a position to cause forward movement of the ram controlled thereby; means for returning said reversing valves to positions to cause rearward movement of said rams; a piston valve element responsive to reverse movement of one of said rams to apply fluid pressure to the reversing valve controlling the movement of such ram; valved passage means establishing a hydraulic connection between said reversing valve elements; and actuating means for the valve in said passage, said actuating means being responsive to the movement of one of said rams at a predetermined stage of operation thereof.

8. A hydraulic system comprising first and second power cylinders with opposed rams; a source of fluid pressure; a control valve mechanism between the pressure source and each power cylinder. each control valve mechanism having a reversing valve element responsive to fluid pressure to move to a position to cause forward movement of the ram controlled thereby; means for returning said reversing valves to positions to cause rearward movement of said rams; selectively operated valve means in the first of said control valve mechanisms for applying fluid pressure to the reversing valve element in said mechanism to initiate a cycle of operation of the first ram; a piston valve element in said first control mechanism responsive to reverse movement of the first ram to apply fluid pressure to the reversing valve controlling the movement of such ram to cause forward movement to be resumed; a valved passage establishing a hydraulic connection between said reversing valve elements; and actuating means for the valve in said passage, said actuating means being responsive to the movement of said first ram at a predetermined stage of operation thereof to establish communication through such passage.

9. A hydraulic system comprising a pair of power cylinders with opposed rams; a source of fluid pressure; control valve mechanism between the pressure source and each power cylinder; a fluid pressure responsive reversing valve element in each control valve mechanism, said mechanisms being oppositely arranged to cause movement of said rams in opposite directions; an additional valve mechanism between said control mechanisms and connected therewith for effecting the simultaneous operation of said reversing valve elements; means responsive to the movement of one of said rams to actuate said additional valve mechanism; an automatic valve means in one of saidcontrol valve mechanisms for repeatedly applying fluidpressure to and releasing it from said reversing valve elements to cause said rams to execute a .plurality of relatively short pressing impulses; and means responsive to the operation of said automatic valve means for interrupting the operation thereof after a predetermined number of pressing impulses have been executed by said rams.

10. A hydraulic system comprising a pair of power cylinders with opposed rams; a source of fluid pressure; control valve mechanism between the pressure source and each power cylinder; a fluid pressure responsive reversing valve element in each control valve mechanism, said mechanisms being oppositely arranged to cause movement of said rams in opposite directions; an additional valve mechanism between said control mechanisms and connected therewith for effecting the simultaneous operation of said reversing valve elements; means responsive to the movement of one of said rams to actuate said additional valve mechanism; an automatic valve means in one of said control valve mechanisms for repeatedly References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,084,149 Larsen June 15, 1937 2,415,603 Muller et a1 Feb. 11, 1947 2,615,306 Alcorn, Jr Oct. 28, 1952 

